Effects of Fiber Dimension and Its Distribution on the Properties of Lyocell and Ramie Fibers Reinforced Polylactide Composites

The regenerated cellulose fiber (Lyocell) and natural cellulose fiber (ramie) with different initial lengths were used to reinforce polylactide (PLA) by melt compounding and injection molding. The fiber dimension and its distribution in composites after injection molding were analyzed by high-resolution Fiber Quality Analyzer (FQA). Moreover, the contents of small fibers with length < 0.2 mm were also provided by FQA. Then the influences of fiber dimension and its distribution on the mechanical properties of the composites were investigated. The results showed that fiber length was reduced during compounding and injection molding processes, and the longer the initial fiber length, the more severe the length declined. Compared with ramie fiber, Lyocell fiber showed a longer fiber length, smaller diameter and narrower width distribution in composite after injection molding. Additionally, the content of small fiber played an important role in the analysis of the relation between the fiber dimension and mechanical properties of composites owing to its smaller aspect ratio. The different mechanical characteristics of the PLA composites were attributed predominantly to the fiber aspect ratio and the small fiber content. By comparison, Lyocell fiber exhibited better reinforcement for PLA due to the higher aspect ratio and lower small fiber content. The tensile strength, tensile modulus and impact strength of Lyocell/PLA composite were increased by 8.61 %, 75.43 % and 26.9 %, respectively.